A typical photographic element contains multiple layers of light-sensitive photographic silver halide emulsions with one or more of these layers being spectrally sensitized to each of blue light, green light and red light. The blue, green and red light-sensitive layers typically contain yellow, magenta, and cyan dye-forming couplers, respectively. To form a color photographic image, the color photographic material is exposed imagewise and processed in a color developer bath containing an aromatic primary amine color developing agent. Image dyes are formed by the coupling reaction of these couplers with the oxidized product of the color developing agent.
Generally, image couplers are selected according to their ability to couple efficiently with oxidized color developer, thus minimizing the necessary amounts of coupler and silver halide emulsion in the photographic element; to provide image dyes whose hues are appropriate for the particular photographic application in which they are to be used; to provide image dyes whose absorption spectra have low unwanted side absorptions and thus lead to good color reproduction; to provide image dyes with good stability to heat, light, and ferrous ions which are present in the bleaching solution; and to provide good physical and chemical properties such as good solubility in coupler solvents, and good dispersibility in gelatin.
In the case of color negative image capture films, the absorption maximum of the image dye should generally be 680 nm or longer, preferably 690 nm or longer, and it should have as little absorption in the green region of the spectrum as possible.
The couplers commonly used to form cyan image dyes in color photographic films and papers are generally of three types, namely, the 1-hydroxy-2-naphthamides represented by formula (A) and described in U.S. Pat. Nos. 2,313,138, 3,002,836, 4,208,210, 5,283,163, 5,380,638, 5,457,008, and 5,476,757; the 2,5-diacylaminophenols and 2-arylureido-5-acylaminophenols represented by formula (B) and described in U.S. Pat. Nos. 2,369,929, 2,895,826, 3,466,622, 3,758,308, 3,864,366, 3,880,661, 3,996,253, 4,333,999, 4,451,559, 4,465,766, and 4,554,244; and the 2-acylamino-5-alkylphenols represented by formula (C) and described in U.S. Pat. Nos. 2,367,531, 2,369,929, 2,423,730, 2,801,171, 3,772,002, 3,998,642, and 4,560,630. These types of couplers can be used either by being incorporated in the photographic silver halide emulsion layers or externally in the processing baths. In the former case the couplers must have ballast substituents built into the molecule to prevent the couplers from migrating from one layer into another. ##STR2##
In each of the formulas (A) and (C), R.sub.1 represents an alkyl or aryl group; in (B), R.sub.1 represents an alkyl, aryl or arylamino group. In (A), (B),and (C), Z represents a hydrogen atom or a group which is split off during the coupling reaction ("coupling-off group"). In (B), R.sub.2 represents an alkyl or aryl group, usually an alkyl group substituted at the alpha position by an aryloxy group. In (C), R.sub.3 represents an alkyl group, usually methyl or ethyl, X represents a halogen atom, usually chlorine or fluorine, and X and Z are usually (but not necessarily) the same.
Although these couplers have been used extensively in color photographic film and paper products, the dyes derived from each of the three types suffer from various deficiencies that make them unsatisfactory for use in color photographic color negative films.
Naphthol cyan couplers of formula (A), in particular the cyan couplers of formula (D), are used primarily in color photographic negative films. In formula (D), Z is usually a hydrogen atom, a chlorine atom, a fluorine atom, an alkoxy group, or an aryloxy group. ##STR3##
The image dyes derived from the couplers of formula (A) have relatively long absorption maxima, generally in the range of 690-705 nm. However, the image dyes derived from these couplers have poor stability to heat and humidity, and to ferrous ions that are present in the bleaching solution.
In recent years the preferred cyan couplers for use in color negative films are the 2,5-diacylaminophenols of formula (B), in particular the 2-arylureido-5-acylaminophenols of formula (E), described in U.S. Pat. No. 4,333,999. In formula (E) Z is usually a hydrogen atom, a chlorine atom, a fluorine atom, or an aryloxy group. ##STR4##
The image dyes derived from the couplers of formula (E) have long absorption maxima, generally in the range of 685-700 nm, which is ideally suited for use in color negative films. Furthermore, the image dyes have excellent stability to heat and humidity and to ferrous ions. While these are substantial improvements over the couplers of formula (A), these couplers have some drawbacks. One serious drawback is that the image dyes derived from them have broad absorption spectra with too much undesirable absorption in the green region. Furthermore, they suffer from poor solubility in common coupler solvents, resulting in coupler crystallization during storage of the dispersions or of the photographic elements in which they are coated. A still further drawback is that they are expensive to manufacture.
The 2-acylaminophenol cyan couplers of formula (C), in particular the couplers of formula (F), are widely used in color photographic papers and color print films. In formula (F) R.sub.3 may be methyl or ethyl. ##STR5##
The couplers of formula (F) are among the least expensive of all cyan couplers to manufacture. They have good solubility in common coupler solvents and good dispersibility, resulting in dispersions with excellent keeping stability and photographic elements that are free of coupler crystallization. These couplers have excellent coupling efficiency. Furthermore, the image dyes derived from these cyan couplers have good stability, particularly ti light. The image dyes have absorption maxima around 630-670 nm. While these properties make them well suited for use in color photographic papers and color print films, their short absorption maxima make them unsuited for use in color negative films.
It is a problem to be solved to provide a photographic element that enables the formation during processing of a cyan dye having a maximum absorbance of at least 680 nm and having a sharp cutting spectrum on the short wavelength side of the maximum.